Preparation of nitrolic acids and pseudonitroles



Patented eb. 27, 1 945 PREPARATION 01 NITROLIC ACIDS AND PSEUDONITROLES Edwin M.- Nygaard, John H. -McCracken, and Thomas T. Noland, Woodbury, N. J asslgnors to Socony-Vacuum Oil Company, Incorporated,

a corporation of New York No Drawing. Application May 29,1943,

Serial No. 489,066

4 Claims.

This invention has to do with anew method for the preparation of nitrolic acids and pseudo-,

nitrolesi It has long been known in the chemical art that other than nitrous acid, and then Separating a nitrolic acid or pseudonitrole from the reaction mixture. While, this method is characterized by the distinct-advantage over prior methods that *diluted' with or added to water. The quantity of nitrous acid is not required as a reactanh'it is further advantageously characterized by the fact that certain valuable by-products, such as oximes, aldehydes and ketones, are obtained therewith.

For example, acetoxime is obtained as a by-prodnitrolic acids and pseudonitroles are prepared by [S uct in the pr p f D DYI pseudonitrole reaction of nitrous acid with primary and secf t D p I ondary nitroparaffins, respectively. For example, Certain p ns Should be Observed in Order a nitrolic acid, such as propyl nitrolic acid, is to a hieve a hi h degree of efliciency h the obtained from primary nitropropane (1-nitro prese t t d. or exa ple, it is desirab e to p an as ill tr t 'by Equation 1; 10 use a stoichiometrical quantity, or a slight ex- Non cess, of a relatively strong alkali with the nitro- H H H v H H l; parafiin reactant; however, a large excess of I OHHNO H g1 alkali is not conducive to the obtainment of good yields of the desired nitrolic acid or pseudoj l 1 pseuomtrolei such as pliopyl l5 nitrole. In this connection, when a 100 per cent pseudomtrole' obta'med from seFondarymtro' excess of 30 per cent sodium hydroxide solution as mustrated, by Was used with Z-nitropropane, the yield of propyl Equatlon pseudonitrole was ,very small. Whil various "3R the N0 strengths of alkali, as alkali metal hydroxides ll 'C? 2+l Oi C +1120 and alkaline earth hydroxides, may be used efiec- "1C tively in the present method, preferred for use are aqueous alkalis havin concentration from These reactions are usually carried out by disabout 10 per t to about 30 per t. l t l v g a r pa afl in aqu a i, t weak alka1is,such as ammonium hydroxide and adding an inorgan c it te d a di y i 25 organic amines, are not contemplated for use in 7 the cold with a mineral acid. Another suggested this th d, for th r a p ently t weakly procedure involves e s ps' ing i r basic to produce. the salts of the nitroparafflns p in water, saturating the su ta Y necessary for the reaction. Accordingly, as used persion with nitrous acid, making the solution h in, th language "relatively strong alkali" Strongly in th an k li metal hy ox e o refers to an alkali metal hydroxide or an alkaline and then acidifying with a mineral acid. earth metal hydroxide, and thus refers to an t should be clear from the foregoing t all alkali suitable for use in the present method. of the methods known to the art for the prepa- Although a nitroparaflin may be contacted with ration of nitrolic acids and pseudonitroles are an alkali at high or low'temperatures,. temperadepe e t po e e Of nitrous i e e tures of the order of 2025 C. are suitable for per se, or developed in the preparation from an thispurpose. Care should be .taken in the acidalkali nitrite and amineral acid. We have, howification treatment so that the temperature ever, now discovered a new method for the prepthroughout this operation be maintained below aration of the aforesaid nitrogen-containing about 15 C; i In general, temperatures from I compounds wherein it is unnecessary to use about 0 to about 5 C. are preferred for the acidnitrous acid or its equivalent in the form of a ification operation. It has been found that if nitrite. t J the temperature of the reaction mixtur is al- Accordingly, the present invention is predicated lowed to increase above about 20 C. during and upon the discovery of a novel method, for-the after the acidification, increasing amount of preparation of nitrolic acids and pseudonitroles. 5 nitrous oxide (N20) are produced and less nitrolic This new method is extremely simple and merely acid or pseudonitrole is found in the reaction involves contacting a nitroparafiln withaqueous product. For the acidification op ra i n. n alkali atasuitable temperature, thereafter-acidimineral acid other than nitrous acid, such as tying the nitroparaflln-alkali mixture at a temhydrochloric, nitric or sulfuric acid, may be used. perature .below about 15 C. with a mineral acid and the strength of such acids-may be varied considerably; It is preferredrhowever, that the mineral acid have such a concentration that no appreciable heat is evolved when the acid is acid used may be varied over, a relatively wide range, but it is desirable to use just a slight excess of acid in the acidification operation. Also, although the nitroparaflin-alkali hydroxide reaction mixture may be added to the mineral acid, or vice versa, in some caseslarger yields have been obtained by adding the nitroparaiiinalkali reaction product to the acid. The preferred procedure, however, is that of adding the reactantsacid and nitroparaflin-alkali hydroxide reaction mixture-simultaneously to cold water, at about C. so that at no time is there an excess of acid or alkali in the reaction mix-' ture. During the acidification operation, it is advantageous to keep oxygen out of the reaction mixture. In this regard, it was found that the yields of pseudonitrole and ketone were appreciably reduced, and the amount of nitroparafiin recovered was correspondingly increased, when oxygen was present in the reaction mixture.

At this time, the reaction mechanism involved in the present method is not completely understood. By way of speculation, however, and not by way of limitation, it is most probable that the reaction proceeds in the manner hereinafter described. When a primary nitroparaffln, as 1- nitropropane, is used as the starting material, the reaction may well be represented by Equation III below:

III

NO ONa H H HaCg-CNO (propyl nitrolic Mild) On the same basis, when a. secondary mtg-:

(inw plume ole) In the speculative Equations III and IV, oxythe reaction. It is most probable that this oxygen, which appears to be necessary to form the .parts by weight of Z-nitropropane.

aldehyde or ketone and the sodium' nitrite, is furnished by an autoxidation and reduction reaction involving the nitroparaflin or, more probably, its sodium salt. This is borne out to some degree by the presence of small quantities of ammonia and oximes in the reaction products; these substances are known to be reduction products of nitroparafiins, Additional foundation for this assumption is evidence furnished by an experiment in which atmospheric oxygen was entirely eliminated during the entire experiment.

The method contemplated herein is useful not only for the preparation of unsubstituted nitrolic acids and unsubstituted pseudonitroles, but is useful as well for the preparation of various substituted compounds of these types. For example, halogen-substituted nitrolic acids and pseudonitroles may be prepared from their correspond-' ing halogen-substituted primary and secondary nitroparafiins, respectively. In general, any. substituent group such as halogen, keto, amino, hydroxyl, etc. may be present on the nitroparafiin reactant, and thus present in the resulting nitrolic acid or pseudonitrole, so long as the substituent group does not interfere with the'formation of thealkali metal salt of the nitroparafiln.

In order to illustrate the present invention, typical pseudonitroles and a typical nitrolic acid were prepared as described in detail in the following examples. Example I is illustrative of the preparation of propyl pseudonitrole, and Examples II--A and IIB are illustrative of the preparation of the same compound in an oxygen atmosphere and a. nitrogen atmosphere, respectively; It will be apparent from the summary of the products obtained in Examples lI-A and 11-3 that the exclusion of oxygen is preferable inasmuch as a larger yield of propyl pseudonitrole is obtained thereby. Examples III and IV, respectively, show the preparation of a typical halogen-substituted pseudonitrole, chloroethyl pseudonitrole, and a typical nitrolic acid, propyl nitrolic acid.

EXAMPLE I Preparation of propyl pseudom'trole Into a three-liter three-necked flask equipped with a stirrer, reflux condenser and a thermometer were placed 290 parts by weight of a 30 per cent aqueous sodium hydroxide solution and 1'78 After the nitroparafiin had gone into solution with some evolution of heat, the solution was refluxed gent- 1y without stirring for 70 minutes. The cool product was a clear, orange-colored, syrupy liquid.

Into another three-liter three-necked flask, cooled with an ice bath and equipped with a, stirrer and two separatory funnels, were placed 400 parts of distilled water. To the cold water were added simultaneously from the two separatory funnels .room overnight to complete the precipitation of the solid. 'I'he solid was filtered onto a Buchner funnel, washed three times with distilled water, and dried in a dwiccator over calcium chloride.

Weight of dried solid was 77 parts by weight. This product proved to be the dimeric form of propyl pseudonitrole. The yield was 65 per cent of the theoretical.

' was 23.8 per cent; nitrogen found on analysis was 24.8 per cent.

The aqueous portion of the reaction product was fractionated through a six-plate column. From this fractionation were obtained:

Boiling Melting Pants by nclght point point Yield C'. C. Percent 33 (acetone). 56. 5-58 57 12 (acetoxime) 56-58. 5 8. 2

The acetoxime was identified by taking a mixed melting with a known sample of acetoxime. There was no depression in melting point.

EXAMPLE II-A Preparation of propyl pseudonitrole in atmosphere Into a two-liter three-necked flask equipped with a thermometer, stirrer and a dropping funnel were placed 840 parts by Weight of a ten per cent aqueous sodium hydroxide solution. Into this solution was slowly dropped 178 parts by weight of 2-nitropropane, keeping the tempera ture between 35 and '40 C., by cooling with a water-bath. The resultant solution was a pale yellow color and was stored at room temperature for three weeks. l

Into a three-necked flask, equipped with a stirrer, aninlet tube for oxygen and two-dropping funnels, was placed 100 parts of distilled water. The water was cooled by means of an ice bath and to the rapidly-stirred water was introduced a stream of oxygen and simultaneously were added from one separatory funnel one-half of the 2- nitropropane-ten per cent sodium hydroxide reaction product, and from the other separatory funnel 170 parts of (1-1) concentrated HCl-HzO. These additions required on hour and fifty minan oxygen utes and oxygen was introduced for another hour..

There was a separation of some solid and a viscous blue-colored liquid. The aqueouslayer was a deep blue color. The entire reaction product was left in a cold room for four days. The aqueous layer was now yellow and was separated from The pure dimer is colorless,- melts to a blue liquid, and then decomposes. Upon gas was used.

nitropropane was recovered by distillation from the water-washed petroleum ether extract- The yields of the various products are summarized in the tabulation given below after Example II-B for comparison with those obtained when nitrogen EXAMPLE II-B Preparation of propyl pseudonitrole in a nitrogen atmosphere In similar equipment to that used in the abovedescribed experiment, the other half of the 2- nitropropane-ten per cent sodium hydroxide reaction product was treated as in the above experiment, with the exception that a stream of oxygen-free nitrogen was bubbled through the reaction mixture in place of oxygen. There was no need to use petroleum ether to precipitate the propyl pseudonitrole in this experiment, as it separated pure and free from any oil. The yield of recovered products from both experiments are summarizedin the following table. Eighty-nine parts by weight of 2-nitropropane were used in Product memwed Oxygen atmosphere Nitrogen atmosphere Parts by Percent "Parts by Percent weight theoretical weight theoretical 2-nltropropahe 37. 5 42.1 9.1 10.2 Propylpseudonitrole. l7. 6 29. 8 35. 4 c0. 0 Acetone l0. 3 35. 6 l7. 6 60. (i Acetone oxime 5. 5 7. 5 8. 6 ll. 8

EXAMPLE III the heavier blue oil and solid. The addition of petroleum ether to the blue oil precipitated a colorless solid. The solid was filtered off and washed with petroleum ether. Ithad a melting point of 75 C. and was found'to be propyl pseudonitrole. The weight of this solid was 17.6 parts by weight, a. yield of 29.8 per cent. I

The petroleum ether extract was washed four times with water and the water-washes combined with the aqueous. layerof the reaction mixture, and the-whole subjected to distillation; acetone, Z-m'tropropane' and acetoxime were isolated in turn. A considerable additional quantity of 2- each experiment.

Yield Preparation of chloroethyl pseudonitrole One mol (109.5 g.) of l-chloro-l-nitroethane was slowly added to 420 grams (1.05 'moles NaOH) of 10 per cent sodium hydroxide solution keeping the temperature at 10 C. The resulting solution was a light-yellow color. To this cold solution, surrounded by an ice bath, was slowly added over a period of one-and-a-half hours dilute H2504 (53.5. parts by wt. cone. H2804 in cc. of H20). The mixture turned a deep blue-green color.

' The product was a very dark blue oil which sepa- One mol (89 g.) 'of l-nitropropane was dissolved in 420 grams (1.05 mols NaOH) of l0 per cent sodium hydroxide solution. The mixture was permitted to stand at room temperature for a considerable time, and was extracted three times with diethyl ether to remove a small quantity of triethylisoxazole. This ether extract was discarded and the filtered aqueous portion reserved.

In a three-necked flask, equipped with a stirrer and two dropping funnels, was placed a little water. The water was cooled to 5-10 C. and to the stirred solution were simultaneously added .over a period of one-and-a-half hours the above filtrate and 268 grams of dilute sulfuric acid (one part or fconc. H2804 to 2.7 parts 01 11:0). The

reaction mixture was kept at a temperature of 5-10 C. The mixture became a light yellowgreen color. A yellow oil was extracted from the This oil gave a blood-red color with 10,per centv sodium hydroxide solution, characteristic of nitrolic acids. 1

The aqueous portion of the reaction mixture was partially distilled through a six-plate column. Propionaldehyde was identified in the distillate as a crystalline derivative formed with 5,5-dimethyl-1, 3-cyclohexanedione, melting point 148-150 C. The melting point'of the same solid prepared from a known sample of propionaldehyde was 150 C. In this case, a mixed melting point was 149.5.0.

From the foregoing illustrative examples, it will be clear that the present method is a valuable means for preparing nitrolic acids and pseudonitroles. As is well known to those familiar with the art, such compounds are valuableintermediates in chemical synthesis; and, recently, these compounds have been found to be extremely effective ignition improvers in Diesel-type fuels. It will also be apparent from the foregoing examples that the present method .provides a means for ob-' taining appreciable yields of valuable chemicals, such as aldehydes, ketones and oximes.

Although the present invention has been illustrated by the preparation of several specific pseudonitroles and a specific nitrolic acid, it is to be understood that these specific embodiments are but representative of the new method for the preparation of compounds of the broad classes of pseudonitroles and nitrolic acids. Accordingly,

the present invention is not to be construed as limited thereto but is to be broadly construed in the light of the defining language in the appended claims.

We claim:

'1. The method of preparation of a compound v selected from the group consisting of nitrolic acids and pseudonitroles which comprises con-' tacting a nitroparaffln selected from the group consisting-of primary and secondary nitroparaffins with substantially a stoichiometrical amount of an aqueous alkali selected from the group consisting of an aqueous alkali metal hydroxide and an aqueous alkaline earth metal hydroxide, then acidifying the nitroparafiln-alkali reaction product so obtained with a mineral acid other than nitrous acid at a temperature below about 15 C. in the substantial absence of oxygen, and separating said compound from the reaction mixture obtained in the preceding operation.

2. The method of preparation of a compound acids and pseudonitroles which comprises contacting a nitroparaifin selected from the group consisting of primary and secondary nitroparaifiins with substantially a stoichiometrical' amount of an aqueous alkali selected from the group consisting of an aqueous alkali metal In!- droxide and an aqueous alkaline earth metal hydroxide, then acidifying the nitroparamn-alkali reaction product so obtained with a mineral acid other than nitrous acid at a temperature below about 15 C. in an atmosphere of nitrogen, and separating said compound from the reaction mixture obtained in the preceding operation.

3. The method of preparation of propyl pseudonitrole which comprises contacting Z-nit-ropropane with substantially a. stoichiometrical amount of aqueous sodium hydroxide, then acidifying the z-m'tropropane-sodium hydroxide reaction product so 'obtainedwith a mineral acid other. than nitrous acid at a temperature below about 15 C. in the substantial absence of oxygen to form propyl pseudonitrole, and separating said propyl pseudonitrole from the reaction mixture obtained in the preceding operation.

4. The method of preparation of propyl pseudonitrole which comprises contacting 2-nltropro-.

pane with substantially a stoichiometrical amount of aqueous sodium hydroxide, then acidifying the Z-nitropropane-sodium hydroxide reaction prodnot so obtained with a mineral acid other than nitrous acid at a temperature below about 15 C. in an atmosphere of nitrogen to form propyl pseudonitrole, and separating said propyl pseudonitrole from the reaction mixture obtained in the preceding operation. EDWIN M. NYGAARD.

JOHN H. McCRACKEN. THOMAS T. ROLAND.

Certificate of Correction Patent No. 2,370,185. I February 27, 1945.

I, EDWIN M. NYGAARD ET AL. It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, first column, lines 58 to 62 inclusive, for that portion of the formula reading and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 19th day of June, A. D. 1945.

LESLIE FRAZER,

Acting Commissioner of Patents.

Certificate of Correction Patent No. 2,370,185. February 27, 1945. EDWIN M. NYGAARD ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, first column, lines 58 to 62 inclusive, for that portion of the formula reading H3O [H HzC H C read 2 0 H1C/ Hgo and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 19th day of June, A. D. 1945.

[SEAL] LESLIE FRAZER,

Acting Commissioner of Patents. 

